Sealing arrangement for the shafts of turbomachines of thermal power plants in which the greater part of a gaseous medium continuously describes a closed cycle under pressure above atmospheric



Oct. 18, 1949. c. KELLER 2,485,447

SEALING ARRANGEMENT FOR THE SHAFTS OF TURBOMACHINES OF THERMAL POWERPLANTS IN WHICH THE GREATER PART OF A GASEOUS MEDIUM CONTINUOUSLYDESCRIBES A CLOSED CYCLE UNDER PRESSURE ABOVE ATMOSPHERIC Filed April 1,1946 Patented Oct. 18, 1949 2,485,447 SEALING ARRANGEMENT FOR THE SHAFTSOF TURBOMACHINES OF THERMAL POWER PLANTS IN WHICH THE GREATER PART OF AGASEOUS MEDIUM CONTINU- OUSLY DESCRIBES A- CLOSED CYCLE UNDER PRESSUREABOVE ATMOSPHERIC Curt Keller, Zurich, Switzerland, assignor to EscherWyss Maschinenfabriken Aktiengesellschait, Zurich, Switzerland, acorporation of Switzerland Application April 1, 1946, Serial No. 658,690In Switzerland September 23, 1940 Section 1, Public Law 690, August 8,1946' Patent expires September 23, 1960 4 Claims.

This invention relates to improvements in a shaft seal for rotatingelements of turbo-machines of thermal power plants, in which thegreatest part of a gaseous working medium continuously describes aclosed cycle under pressure above atmospheric pressure, whereby theworking medium, the temperature of which has been raised by a supply ofheat from an outside source, is allowed to expand in at least oneturbine while giving up energy externally, after which it is againbrought to a higher pressure in at least one turbo-compressor.

In a plant of the above mentioned type it is particularly important thatleakages of the working medium are prevented as far as possible at theplaces where the shafts of the turbo-machines are sealed from theatmosphere; since any losses of working medium may afiect verydetrimentally the efiflciency of the plant. The proper sealing of theshafts in such plants presents great dimculties, as the pressureprevailin in the entire closed circuit substantially exceeds atmosphericpressure. Thus, the pressure prevailing at the point where the pressureof the whole circuit is lowest, may still amount to 10 atmospheres,whilst at the point of highest pressure within the circuit, toatmospheres may prevail. In contrast thereto the highest pressureoccurring in gas turbines working on the principle of the open circuitis, as is well known, never higher than 3 to 4 atmospheres, whilst thelowest pressure encountered is about atmospheric. In thermal powerplants working on the principle of the closed circuit, leakages ofworking medium should be prevented as far as possible since any gasescaping from the circuit must be replaced, and the fresh gas to beintroduced into the circuit has to be compressed at least up to thelowest pressure prevailin within the-circuit. This lowest pressure can,as already stated, amount to 10 atm. and more. Accordingly a relativelygreat amount of energy is required to bring the make-up working medium,preferably air of atmospheric pressure, to the pressure prevailing atthe point where said make-up working medium is introduced into thecircuit. The additional energy required for this purpose necessarilyinvolves a corresponding deterioration of the efficiency of the wholeplant.

The solution of the problem in question is made particularly difficultby the following three facts: the high pressure of the working mediumcirculating in the closed circuit, the prevailing high temperatures (upto 650 C.), particularly those at the high-pressure end of the turbine,and the requirement that the auxiliary media used for sealing purposesmust be prevented from passing through the stuffing box into the closedcircuit of the plant. These various difliculties are overcome accordingto the present inventionby supplying at least to the stufling boxes ofthe turbine as sealing medium gas tapped from the circuit of the primaryworking medium at a place where a higher pressure prevails than in theinterior of the respective stufiing box, and by associating with each ofsaid stufiing boxes a bearing space sealed against the atmosphere by aliquid. Each of these bearing spaces is then connected to a receptaclein which the sealing gas separates from the sealing liquid, the gasspace of this receptacle being connected to a point of the closedcircuit at which a lower pressure prevails than at the tapping point ofthe sealing gas for the respective stuiiing box, whilst the liquid spaceof said receptacle is connected to a pump supplying the sealin liquidfor the bearing space allotted to the respective stuifing box.

The regulation or governing of load fluctuations which arise in plantsof the kind in question is usually effected by changing the density ofthe working medium describing the closed cycle approximatelyproportionally to the momentary power delivered externally by theturbine, the speeds of the turbine and compressor being maintainedunchanged. When governing in such a manner the pressures at diiferentpoints in the cycle vary approximately proportionally to the momentarypower delivered externally by the turbine, so that when the object ofthe present invention is embodied in such a plant, the pressure of thesealing gas supplied to the stufling boxes from the circuit described bythe working gas of the plant automatically adjusts itself to the load ofthe plant, 1. e. to the density of said gas. Thus, in principle, neitherspecial governing means' for adjusting to the load of the plant thepressure of the sealing gas to be supplied to the stuffing boxes nor aspecial compressor for producing the required sealing gas pressure arerequired. In this way it is possible to reduce the erating staff. Allthis is 'mainly due to the fact that the ratio between the sealing gaspressure in the respective stumng box and the pressure of the gas in theclosed circuit remains the same at all loads of the plant, since onlythe absolute values of the respective Dtwures vary but not theirrelationship to one another. The directions of flow of the differentcurrents of sealing gas andseaiing liquid therefore remain unchanged atall loads of the plant, which is of particular importance.

In the accompanying drawing, a typical embodiment of the invention isillustrated.

In the figures .Fig. 1 illustrates in diagram 8. thermal power plant inwhich air continuously describes a closed cycle under pressure aboveatmospheric and in which the turbine is provided with a sealingarrangement according to the present invention.

Fig. 2 shows details of Fig. 1 on a larger scale.

Referring to the drawing, reference I denotes a heater, in which heat issupplied to air describing for the greater part a closed cycle at apressure above atmospheric. To this heater l fuel is supplied throughpiping 2 and combustion air through piping 3. The air heated in thismanner passes to a multi-stage air turbine of the axial flow type, inwhich it expands, thereby giving up energy to a generator 6 and to arotary compressor I which may be, for instance, of the axial flow .type.The air issuing from the turbine 5 passes through a piping 8 into a heatexchanger 3 liesigned as a countercurrent apparatus, where it gives upheat to that part of the working medium which is supplied at a higherpressure to said heat exchanger 8 from the axial flow compressor 1through piping it. This last mentioned part of the working medium flows,after it has been heated in the heat exchanger 8, through a piping Ii tothe heater I.

Referencev i2 denotes the part of the turbine shaft that has to besealed on the high pressure side of the air turbine 5, and 13 the partof said shaft to be sealed on the low pressure side. Further, referenceI4 denotes the part of the shaft of the axial flow compressor 1 whichhasto be sealed on the suction side and [5 the part of said shaft to besealed on the pressure: side of the compressor. To the stufllng boxes l5and I! (see particularly Fig. 2) provided for sealing the parts i2 andII respectively, of the turbine shaft, air tapped from the closedworking circuit of the plant is supplied as a sealing medium. Such airis tapped from the circuit at a point at which a higher pressure than inthe interior of the respective stumng boxes l8 and i1 prevails. In orderthat such sealing medium may be supplied, a piping i8 connects ahigh-pressure stage of the compressor 1 to the interior of the stuflingbox l5, and a piping l9 connects a stage of a lower pressure of thecompressor I to the interior of the stufllng box H. The sealing airescaping outwards through the stuffing box I! passes into a space 2i(Fig. 2), whilst the sealing air escaping outwards through the stuffingbox i8 passes into a space 28 which is sealed against the atmosphere bya liquid sealed stuiling box 22. Sealing liquid is supplied to thelatter by a pump 24 through a piping 23; a part of the sealing liquiddelivered by the pump 24 also passes into a bearing 25 for the turbineshaft, the bearing 25 being arranged adjacent to the stuffing box 212.The sealing assess? liquid escaping inwards through the stuffing box 22collects in the space 28 from which it flows,

together with the sealing air also escaping intothis space, through apiping 28 into a receptacle 21, Where the sealing air separates from thesealing liquid. This air flows back to .the circuit traversed by theworking medium of the power plant through a piping 28, which terminatesat a point in the interior of the compressor 1 where a lower pressurethan at the tapping pointof the sealing air for the stuffing box I8prevails. The liquid space of the receptacle 2! is connected to the pump24 through a piping 29. The sealing liquid escaping outwards through thestuillng box 22 and the bearing passes into a space 30 (Fig. 2-) fromwhich it flows away through a piping 3i into a collecting tank 32 whichis subdivided by intermediate walls into compartments.

atmosphere in a similar manner by a stumng box 33 supplied with sealingliquid by a pump "through; piping 34. A part of the liquid supplied bytlie pump 35 also passes into a bearing 36 for the turbine shaftarranged adjacent to the stuffing box 33. The sealing liquid escapinginwards through the stuiling box 33 collects in the space 2| where itmixes with the sealing air escaping through the stufllng .box I] alsointo said space 2i. The resulting mixture flows from the space 2ithrough a piping 31 into a receptacle 38 where the sealing air againseparates.from the sealing liquid. The former returns through a conduit38 into the circuit of the working medium of the plant, since saidconduit terminates at a place inth'e' interior of the compressor 1 wherea lower pressure prevails than at the place where the sealing air forthe stufllng box I! is tapped. The liquid space of the receptacle 38 isconnected through a piping 40 to the pump 35. The liquid escapingoutwards through the stufling box 33 and the bearing 38 passes to aspace 4| (Fig. 2), from which it flows away through a piping 42 into acompartment of the collecting tank 32.

The stuillng box sealing the section i5 of the compressor shaft issupplied, in the embodiment illustrated, only with sealing liquiddelivered by a pump 43 through a piping. 44. The sealing liquid escapinginwards through the stuffing box 45 mixes with air which escapes alongthe shaft section i5 of the compressor 1. The resulting mixture of airand liquid flows through a piping 45-into the receptacle 4'! where theair separates again from the sealing liquid. The separated air flowsback through a piping 48 to'the circuit of the working medium of theplant, whilst the liquid separated in the receptacle 4| flows back tothe pump 43 through a piping 48. The part of the sealing liquid escapingoutwards in the stuffing box 45 flows through a piping 50 into acompartment of the collecting tank 32.

The stumng box 5i on the suction side of the compressor 1 likewise onlyreceivessealing liquid from a pump 52 through a piping 53. The sealingliquid mixing in the stuffing box 5i with the air escaping along theshaft section i 4 flows away through a piping 54 into a receptacle 55where the air again separates from the liquid. The action produced by anozzle 55 causes the air separated in the receptacle 55 to flow backthrough a piping 58 into the suction pipe of the compressor 1, whilstthe sealing liquid returns through a piping 51 to the pump 52. Thesealing liquid escaping outwards in the stuffing box 5i flows through aD ning 58 into a compartment of the collecting tank 32.

In order that the receptacles 21, 38 41 and 55 can serve simultaneouslyas liquid coolers, coils 21 38 and 55 respectively, are provided. Thesecoils are connected to a common piping 59 supplying a cooling medium.The reference 60 denotes pumps which force the sealing liquid collectedin the tank 32 back into the receptacles 21, 38, 4! and 55. Reliefvalves are applied to the discharge lines of these pumps to limit thedelivery pressure. The relief valves are identified by legends onFig. 1. The reference numeral 6| denotes an auxiliary pump forcingsealing liquid into the different stufling boxes when the plant isstarted up. The pumps 60 and pumps 24, 35, 43 and 52 are driven as aunit by one motor as shown and the pump 6| by another motor 63.

Owing to the fact that the stufling boxes i6 and I! of the turbinereceive through pipings l8 and i9 respectively, air tapped from thecircuit of the thermal power plant, a sealing gas pressure isautomatically set up in these stufling boxes which is alwaysproportional to the momentary load of the power plant. As a result ofthis fact, losses of working medium at the stufling boxes of the airturbine 5 are prevented in a simple manner. Thereby the sealing air forthe stufling boxes is tapped from a point of the circuit de-.

scribed by the working medium where a low tenfperature prevails, so thatwhen using, for instance, oil as sealing liquid the latter will notignite when it comes in contact with sealing air. Since to each stuflingbox of the rotary machines is also allotted a liquid seal, practicallyno air can escape from the air circuit of the power plant into theatmosphere.

The hereinbefore described sealing means only involves small losses ofenergy, since only little pressure is lost when sealing air escapesthrough the stufiing boxes.

Where necessary, throttling means may be provided in order to regulatethe quantity of sealing air supplied to the stuffing boxes from thecompressor in such a manner that only just the re quired minimumquantity of sealing air passes through the stuffing boxes. The reference62 denotes such means.

What I claim is:

1. In a shaft sealing arrangement for turbomachines of thermal powerplants, in which the greater part of a gaseous medium continuouslydescribes a closed circuit under pressures above atmospheric pressure,and in which circuit, compressed working medium, the temperature ofwhich has been raised by a supply of heat from an outside source, iscaused to expand in at least one turbine while giving up energyexternally, after which it is again compressed in at least oneturbo-compressor; the combination of shaftsealing stuffing boxes of thegas-sealed type; means for supplying to said stuffing boxes, as thesealing medium, gas tapped from said closed circuit at a point where ahigher pressure prevails than that against which the respective stuflingbox seals; means including liquid seals for isolating from theatmosphere spaces at the outer ends of said gas-sealed stuffing boxes;means for supplying sealing liquids to said liquid seals; separators forgas and liquid associated with respective isolated spaces; means forsupplying the gases separated in said separators to at least one pointin said closed circuit at which prevails a lower pressure than that atthe tapping point of the sealing gas for respective gas-sealed stufllngboxes, and means for supplying the liquid separated in each separator torespective liquid seals.

2. In a shaft sealing arrangement for turbomachines of thermal power.plants, in which the greater part of a gaseous medium continuouslydescribes a closed circuit under pressures above atmospheric pressure,and in which circuit, compressed working medium, the temp e f which hasbeen raised by a supply of heat from an outside source, is caused toexpand in at least one turbine while giving up energy externally, afterwhich it is again compressed in at least one turbo-compressor; thecombination of shaft sealing stuffing boxes of the gas-sealed type;means for supplying to said stufiing boxes, as the sealing medium, gastapped from said closed circuit at a point where a higher pressureprevails than that against which the respective stufling box seals;means comprising combined shaft bearings and stuffing boxes serving toisolate from the atmosphere spaces at the outer ends of respectivegas-sealed stufling boxes; means serving to supply sealing liquids toeach of said combined bearings and stufling boxes; gravity gas andliquid separators associated with respective isolated spaces; meansconnecting each separator to discharge separated gas to at least onepoint in said closed circuit at which prevails a lower pressure thanthat at the tapping point of the sealing gas for respective gas-sealedstufling boxes; and means connecting each separator to discharge liquidto respective means serving to supply sealing liquid.

3. In a shaft sealing arrangement for turbomachines of thermal powerplants, in which the greater part of a gaseous medium continuouslydescribes a closed circuit under pressures above atmospheric pressure,and in which circuit, compressed working medium, the temperature ofwhich has been raised by a supply of heat from an outside source, iscaused to expand in at least one turbine while giving up energyexternally, after which it is again compressed in at least oneturbo-compressor; the combination of shaftsealing stufling boxes of thegas-sealed type;

means for supplying to said stufiing boxes, as

the sealing medium, gas tapped from said closed circuit at a point wherea higher pressure prevails than that against which the respectivestuffing box seals; throttling means for adjusting the rate of supply ofsaid sealing gas; means including secondary shaft seals of theliquidsealed type, serving to isolate from the atmosphere spaces at theouter ends of respective gassealed stuffing boxes; means for supplyingsealing liquid to each of said secondary shaft seals; gas and liquidseparators associated with respective isolated spaces, each separatorhaving a gas space and a liquid space; means connecting the gas space ofeach separator to a point of said closed circuit at which prevails alower pressure than that at the tapping point of the sealing gas for therespective gas-sealed stuiiing box; and means connecting the liquidspace of each separator to respective means for supplying sealingliquid.

4. In a shaft sealing arrangement for turbomachines of thermal powerplants. in which the greater part of a gaseous medium continuouslydescribes a closed circuit under prl. sures above atmospheric pressure,and in which circuit compressed working medium, the temperature of whichhas been raised by a supply of heat from an outside source, is caused toexpand in at least one turbine while giving up energy ex- 7 ternally,after which it is again compressed in at least one turbo-compressor; thecombination oi shaft-sealing stumng boxes of the gas-sealed type: meansfor supply tosaid stuning boxes,

as the sealing medium, gas tapped from said closed circuit at a pointwhere a higher pressure prevails than that against which the respectivestufling box seals; means comprising combined shait bearings andstufling boxes serving to isolate from the atmosphere spaces atthe-outer i0 ends of respective gas-sealed stumng boxes: pumps servingto supply a sealing liquid to each 01' said combined bearings andstufling boxes; gas and liquid separators in communication withrespective isolated spaces and each having a gas space and a liquidspace; means connecting the gasspace or each separator to a point ofsaidclosed circuit at which prevails a lower pressure than that at thetapping point 01 the sealing gas for the respective gas-sealed stumngbox; and means connecting the liquid space 0! each separator to acorresponding one or said pumps.

CURT KELLER.

REFERENCES CITED The loliowing references are oi record in the tile ofthis patent:

' Um'rm s'm'ms PATENTS Number Name Van Rijswiik May 20', 1930Certificete of Correction Patent No. 2,485,447 October 18, 1949 CURTKELLER It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction asfollows:

Column 7, line 4, for the word supply? read supplying;

and that the said Letters Patent should be read with this correctiontherein that the same may conform to the record of the case in thePatent Office. Signed and sealed this 7th day of February, A. D. 1950.

. THOMAS F. MURPHY,

Assistant commissioner of Patents.

